A network protocol used when communication is carried out through a single wire bus such as LIN (Local Interconnect Network) is known. In case of LIN, the network is mainly installed on a car and is used to control various devices such as a door mirror and a door lock.
In LIN, the waveform of a signal to be inputted and outputted to or from the bus is standardized to meet various conditions. A duty ratio is contained in these conditions and the duty ratio is a ratio of a time for the signal to be higher than a predetermined voltage and a time for the signal to be lower than the predetermined voltage. The duty ratio varies according to a change of the environment of the LIN, and there is a case that the signal waveform comes off a range of the standard.
In case of LIN, a car-mounted battery is used as a power supply to supply a bus with a voltage. It is known that the power supply voltage of the car-mounted battery varies largely between 7 V and 18 V while a charging operation or a discharging operation is carried out, even when a ruled voltage is 12 V. Also, a variation of the duty ratio is sometimes caused through a variation of the total load connected with the bus.
Patent Literature 1 discloses an output circuit of an LSI. The output circuit of the LSI detects a dull waveform at the time of rising of a signal and the time of falling thereof and adjusts the waveform of the next signal based on the detection result.